1. Field of the Invention
This invention relates to the treatment of plant seeds and, to compositions for use in such methods, in particular, it relates to methods and compositions useful for cleaning, scarifying, and improving the germination rate processability of plant seeds.
2. Description of the Art
Seeds of essentially all varieties are often treated by one or more procedures to improve their quality and utility for a variety of uses such as storage, planting, oil-extraction, and subsequent processing for the manufacture of seed-derived products such as animal foods, including human foods. Although most seeds are treated after harvest, some are treated before harvest by the application of chemicals that promote maturation or that facilitate harvesting or accelerate germination.
Residual mineral and organic matter, particularly residual plant matter which is not an integral part of the seed husk or hull, is most often removed from seeds intended for storage or subsequent use. The presence of such residual organic matter interferes with handling apparatus and procedures, promotes spoilage through the growth of bacteria and fungus, fouls the extraction products from certain seeds such as oils from cotton seeds and the like, and can inhibit germination in seeds that are replanted.
Current procedures for the removal of residual plant matter and other organic and/or mineral matter from plant seeds include washing with water or other solutions, mechanical abrasion, and treatment at elevated temperatures with strong base such as calcium hydroxide, sodium hydroxide, and the like. Seeds that are intended for replanting are often treated to improve their germination rate, i.e., to reduce the time required for seed germination after planting. Current practices for increasing germination rate involve scarifying the seeds, by mechanically scraping or chemically treating the seed husk to increase its permeability to moisture. Treatment with strong base increases the permeability of the seed covering (which consists principally of cellulose and lignand) by partially dissolving or modifying the seed covering. Increased germination rate minimizes the risk of disease or parasite infestation prior to germination and often facilitates better timing of crop emergence and maturation.
Similar mechanical and caustic treating procedures are employed to clean and/or beneficiate seeds prior to extraction of oil or other seed products. Such treatments reduce the amount of energy required to recover oil from seeds by compression and/or increase the rate at which such oils are extracted. Plant seeds also are processed to improve their value as food for domestic animals and for the manufacture of (1) processed foods such as processed rice, wheat and other grains, (2) foods that require less cooking time for their preparation, (3) other seed-derived food products such as cereals, bakery products, flour, corn meal, etc., and (4) certain seed-derived vegetable products such as corn syrup, and soy bean meal and other vegetable protein concentrates.
Contemporary mechanical seed-treating methods such as mechanical scarification involve the use of relatively complicated equipment and the expenditure of mechanical energy. They do not always result in equal or homogeneous scarification and/or cleaning of all seeds and thus can produce a heterogeneous product. Furthermore, the necessity for complex mechanical equipment requires that the raw seeds be shipped to a location at which such equipment is available. The chemical treating methods such as hot caustic treatment involve the use of substantial amounts of caustic reactants which are often consumed in the process. Such methods also require elevated temperatures, and thus excessive energy input, and relatively long contact times.
It is known that sulfuric acid will chemically react with vegetable matter. However, sulfuric acid is such a strong oxidizing and sulfonating agent that it cannot be employed for seed treatment without also oxidizing and/or sulfonating desirable portions of the seed product.
Combinations of urea and sulfuric acid are also known and have been used in the agricultural industry primarily when the simultaneous addition of urea and sulfur to the soil is desired. It is also known that urea and sulfuric acid will combine to form adducts including the monourea-sulfuric acid adduct and the diurea-sulfuric acid adduct. For instance, D. F. du Toit, Verslag Akad. Wetenschsppen, 22, 573-4 (abstracted in Chemical Abstracts, 8, 2346, 1914) disclosed that urea forms certain compounds with oxalic, acetic hydrochloric, nitric and sulfuric acids. L. H. Dalman, "Ternary Systems of Urea and Acid. I. Urea, Nitric Acid and Water. II. Urea, Sulfuric Acid and Water. III. Urea, Oxalic Acid and Water"; JACS, 56, 549-53 (1934), disclosed the phase relationships between the solid phase and saturated solutions containing urea and sulfuric acid at 10.degree. C. and 25.degree. C. The Sulfur Institute, Sulfur Institute Bulletin No. 10 (1964), "Adding Plant Nutrient Sulfur to Fertilizer", disclosed that urea reacts with sulfuric acid to form two complexes of "urea sulfate" which are useful fertilizers. Methods of manufacturing certain combinations of urea and sulfuric acid are disclosed by Verdegaal et al. in U.S. Pat. No. 4,310,343 and by Jones in U.S. Pat. No. 4,116,664. However, neither these nor other investigators recognized that urea-sulfuric acid compositions containing a significant proportion of the monourea adduct of sulfuric acid are uniquely active toward organic materials such as residual organic matter contained on plant seeds and the husks or hulls of the plant seeds, or that the diurea adduct of sulfuric acid exhibits little, if any, of such activity.
Accordingly, a need exists for improved processes for treating plant seeds, and particularly for improved processes for cleaning and/or scarifying plant seeds, for increasing the germination rate of plant seeds, and for improving the quality of plant seeds for use in the manufacture of seed-derived products such as vegetable oils, vegetable protein concentrates, and food products.
It is therefore a principal object of this invention to provide novel methods for treating plant seeds.
Another object of this invention is the provision of methods for cleaning plant seeds.
Yet another object of this invention is the provision of methods for scarifying seeds.
Another object is the provision of methods for increasing the germination rate of plant seeds.
Yet another object of this invention is the provision of methods for improving the storage-stability of plant seeds.
Yet another object of this invention is the provision of methods for improving the quality of plant seeds for the manufacture of seed-derived products.
Another object is a provision of methods for improving the oil-extractability of oil-containing plant seeds.
Yet another object is the provision of methods for improving the processability of plant seeds for the manufacture of food products.
Another object is the provision of methods of extracting oil from oil-containing plant seeds.
Yet another object of the provision of novel seed-containing compositions.
Another object is the provision of seed-containing compositions suitable for use in the manufacture of improved plant seeds.
Yet another object is the provision of seed-containing compositions suitable for use in the manufacture of seed-derived products such as vegetable oil and food products.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawing and the appended claims.